Tile Quantity

Tile quantity starts as division — area ÷ tile area — and everything that goes wrong is in the allowance.

Waste by pattern

Straight or running bond 10%. Diagonal 15%. Herringbone 20%. Add 5% for a room with alcoves, an island, or many door openings.

Diagonal and herringbone waste more because nearly every perimeter tile takes two cuts, and a two-cut offcut fits nowhere else.

Large-format tiles waste more at any pattern: a 24 × 48 in tile cut to fill a 6-inch strip loses most of the tile, where the same strip in 6 × 6 loses almost nothing.

Buy from one lot

More important than buying the exact number. Ceramic and porcelain are fired in batches and color varies measurably between runs — the shade number is on every box, and tiles from two lots in one floor show as a visible change part way across the room.

Keep the leftovers. A cracked tile in three years cannot be matched from a shop.

Grout is a different calculation entirely

Grout depends on joint length, which is set by tile size. A 2 × 2 in mosaic has roughly twelve times the joint per square foot of a 24 × 24 in tile — same room, twelve times the grout. Joint width and tile thickness scale it further.

Thinset depends on the trowel

And the trowel depends on the tile: 1/4 × 1/4 in notch for tile up to 8 in, 1/2 × 1/2 in for 12 to 16 in, larger above that. ANSI A108.5 requires 80% mortar contact for dry floors and 95% for wet areas — that is the specification the notch choice has to satisfy.

Tile over about 15 inches also needs back-buttering, which adds 30 to 40% to thinset consumption. Budget it rather than discover it.

Porcelain or ceramic

One measured property separates them: porcelain absorbs 0.5% or less of its weight in water. Everything else — frost resistance, density, stain resistance, price — follows from that.

PEI rates the glaze surface, not the body, and says nothing about frost resistance or absorption.